1. Field of the Invention
The present invention relates to an actuator, and more particularly, to an actuator that can be designed in a compact size by using a substrate (hereinafter referred as “focusing-substrate”) provided with a focusing coil pattern to maximize the space efficiency, and of which assembling process can be simplified. Further, the present invention relates to the actuator.
2. Description of the Related Art
Generally, an optical pickup actuator is used for a variety of optical players such as a mini disk player (MDP), a compact disk player (CDP), and a laser disk player (LDP). The optical pickup actuator is vertically disposed under an optical media such as a disk of the optical player to (a) detect a desire track location of the disk while linearly moving in a radial direction of the disk, (b) transmit laser light to a pit recorded on a surface of the disk at the detected track location, (c) detect reflection light received through an optical system, and (d) convert the detected reflection light into an electric signal so as for a user to listen to and/or watch sound and/or image data of the recorded pit through the optical players.
FIG. 1 schematically shows a conventional optical pickup device.
As shown in the drawing, a conventional optical pickup device 10 is installed on main and auxiliary shafts 3 and 5 that are provided on a deck panel 1 of an optical driver to record signals on an optical disk D or playback the signals recorded on the optical disk D while moving in a direction of a shaft axis.
The optical pickup device 10 includes a base 30 coupled on the main and auxiliary shafts 3 and 5 to reciprocally move along the direction of the shaft axis and an actuator 20 disposed on a top of the base 30 to converge incident light beams and focus the converged light beams on a point of the optical disk while moving together with the base 30.
FIG. 2 shows the actuator depicted in FIG. 1.
As shown in the drawing, the conventional optical pickup actuator 20 includes a blade 22 and an object lens 21 disposed on a top of the blade 22. Focusing and tracking coils 23 and 24 are wound such that the blade 22 can be minutely moving in focusing (vertical) and tracking (horizontal) directions. Magnets 27 for generating electromagnetic force and a yoke 28 are disposed in the vicinity of the focusing and tracking coils 23 and 24.
The blade 22 is elastically supported on a wire holder 26 by wires 25 horizontally extending in the tracking direction. That is, first ends of the wires 25 are fixed on both sides of the blade 22 by soldering and second ends thereof are fixed on the wire holder 26. By elastic force of the wires 25, the blade 22 can minutely move in the vertical and horizontal directions.
When electric power is applied to the coils 23 and 24 through the wires 25, the object lens 21 moves in the focusing or tracking directions by the electromagnetic force.
Such an actuator module using the coils is well known in the art. That is, in order to move the blade, the coils are used for generating Lorenz Force. When current is applied to the coils formed of a copper wire, Lorenz Force is generated by magnetic field formed by permanent magnets to move the blade in the vertical and horizontal directions. At this point, in order to adjust the motion in the vertical and horizontal directions, a plurality of coils are disposed together with the permanent magnets.
With electronic devices being small-sized, there has been a need of an actuator that can be applied to a small, slim electronic device. However, in the conventional actuator, since the coils are wound to be disposed on a side surface of the blade, there has been a limitation in reducing the size of the electronic device. Furthermore, since the conventional actuator is composed of many components, the manufacturing process is so complicated and a defective rate of the manufacture products is increased.
To solve the above problems, Korean Patent Application No. 2001-42407 discloses an actuator having a substrate (hereinafter referred as “Tracking-substrate”) having a pattern corresponding to the tracking coil. Therefore, there is no need of installing the tracking coil, improving the productivity and reducing an overall thickness of a tracking part. That is, the actuator is helpful in reducing a device where it is employed.
FIG. 3 is an exploded perspective view of a conventional improved optical pickup actuator and FIG. 4 is a perspective view of a tracking-substrate depicted in FIG. 3.
Referring to FIG. 3, there is shown such a conventional improved actuator.
As shown in the drawing, the actuator includes focusing driving means and tracking driving means so that a blade 32 provided with an object lens 30 can move the object lens 30 in the focusing and tracking directions in response to focus of the optical beams.
The focusing driving means includes a focusing coil 34 to drive the blade 32 in a focusing direction with respect to a direction of an optical axis of the object lens 30. The tracking driving means includes a tracking-substrate 50 having a pattern corresponding to the tracking coil to drive the blade 32 in a tracking direction perpendicular to the focusing direction.
That is, the focusing coil 34 is wound around an outer circumference of the blade 32 to minutely move the object lens 30 in the focusing direction. The tracking-substrate 50 is formed to be flexible and attached on front and rear surfaces of the blade 32 to minutely move the object lens 30 in the tracking direction.
The tracking-substrate 50 includes a first tracking part 52 attached on the front surface of the blade 32, a second tracking part 54 attached on the rear surface of the blade 32, and a connecting part 56 for connecting the first tracking part 52 to the second tracking part 54.
At this point, it is preferable that a width of the connecting part 56 is less than those of the tracking parts 52 and 54. Formed on upper and bottom portions of the connecting part 56 are respectively soldering parts 58 and 59.
The first tracking part 52 is provided with first and second patterns 60 and 62 that are spaced at a predetermined interval. The second tracking part 54 is also provided with third and fourth patterns 64 and 66 that are spaced at a predetermined interval. All of patterns are interconnected by a single wire. That is, a coil extends from the upper soldering part 58 to the lower soldering part 59 while forming the first, second, third and fourth patterns 60, 62, 64 and 66.
Provided around the blade 32 are magnets 38 and a yoke 40 that generate electromagnetic force. The blade 32 is elastically supported on the wire holder 44 through wires 42. That is, first ends of two pairs of wires 42 are connected on each of first and second sides of the blade 32 and second ends of the two pairs of wires 42 are fixed on the wire holder 44. Therefore, the blade 32 can minutely moves by the elastic force of the wires 42 in vertical and horizontal directions.
The wires 42 of the first side of the holder 44 are earthed on a pattern formed on the soldering parts 58 and 59 of the tracking-substrate 50 to be connected to the blade 32. The wires 42 of the second side of the holder 44 are connected to the blade 32 through the focusing coil 34. When electric power is applied to the wire 42, current flows along the focusing coil 34 and the tracking-substrate 50. As a result, the actuator moves in a focusing or tracking direction by the electromagnetic force.
The operation of the above-described conventional actuator device will be described hereinafter.
When electric power is applied through the wire 42, current flows along the focusing coil 34 and the patterns of the tracking-substrate 50, generating electromagnetic force by which the blade 32 provided with the object lens 30 minutely moves in the vertical and horizontal directions. A moving distance and direction of the blade 32 can be adjusted by adjusting a current flowing direction.
According to the above-described actuator, since the tracking coil is not wound directly on the blade but the tracking-substrate 50 provided with a pattern defined in an identical shape to the conventional tracking coil is attached on the blade 32 as shown in FIG. 4, the assembling process can be simplified, saving the working time. That is, since a process for winding the tracking coil can be omitted, the number of overall processes can be reduced, improving the productivity, reducing the defective rate and saving the equipment costs for manufacturing the actuator.
Furthermore, the tracking-substrate 50 allows the overall thickness of the actuator to be reduced, resulting in reducing a gap between the magnets 38 and the yoke 40. That is, while the tracking coil has a 0.7-0.8 mm thickness, the tracking-substrate has a 0.2-0.3 mm thickness, reducing the gap by 0.4 mm.
According to the improved technique, since a process for winding the tracking coil can be omitted, the number of overall processes can be reduced, improving the productivity, reducing the defective rate and saving the equipment costs for manufacturing the actuator. Furthermore, the tracking substrate reduces the overall size of the actuator.
However, in order to provide reasonable tracking sensitivity, an effective length of the magnetic field of the tracking part should be higher than a predetermined length. Therefore, the tracking-substrate should be lengthened in a vertical direction, making it difficult to reduce the size of the actuator. Further more, since two pieces of the tracking-substrates are used, there is an limitation in reducing the manufacturing costs.
To solve the problems, a technique for forming the focus and tracking coil patterns on a single substrate has been proposed. However, in this case, a sufficient tracking sensitivity cannot be obtained.
That is, in order to obtain a sufficient tracking sensitivity, a thickness of the tracking coil pattern should be 0.7-0.8 mm. In this case, the manufacturing costs are increased.